Download Alaska’s Thawing Permafrost

Alaska’s Thawing Permafrost
In this Landsat satellite image of Cape Halkett, Alaska, a landscape of thawing permafrost appears like a section of white and grey bone,
full of openings. Blue and green indicate where open water has increased from 1955 to 2005. Smaller areas of reddish orange show land
gained. Landsat gives us a special vantage point to monitor changes in the landscape over time. Image credit: Mars/Houseknecht, USGS.
www.nasa.gov
Melting Permafrost Causes Coastal Erosion
Goddard Space Flight Center
The low-lying Arctic coastal plain of Alaska north of
Teshekpuk Lake on the Beaufort Sea hosts endangered
species of waterfowl, provides calving grounds for large
herds of caribou, and contains potentially significant
petroleum resources. For tens of thousands of years,
underlying this special place has been permafrost—
defined as permanently frozen ground that remains at or
below 0º C (32º F) for at least two years at a time. Not
only wildlife, but people too, have built their lives and
livelihoods on permafrost in Alaska. Roads, buildings,
and pipelines rest and rely on hard permafrost foundations. But permafrost is sensitive to climate change, and
powerful warming forces are at work.
Continuous permafrost on the North Slope of Alaska
has warmed 2.2–3.9º C (4–7º F) over the last century.
Thawing permafrost is more prone to erosion, and
erosion means the loss of land. Thawing also produces
excessive wetting and plasticity and makes sediments
unstable. Thawing of permafrost and cycles of freezing
and thawing cause extensive damage to highways, railroads, airstrips, and other facilities. Many native villages
are located on low-lying rivers and coasts where they
may be susceptible to erosion due to melting permafrost. Combating eroding community infrastructures
takes time and labor away from the activities required
for survival.
Governments and communities are concerned about
these changes. To make the images on the other side of
this lithograph, scientists at the U.S. Geological Survey
analyzed Landsat data and topographic maps compiled
from aerial photographs. They found that land loss in
the study area more than doubled from 1985–2005,
compared to the 30-year span from 1955–1985. In some
areas, coastal erosion has caused the shoreline to recede
as much as 0.9 km (0.56 mi) over the last 50 years.
“This area’s increased rate of coastal erosion over these
time increments may be the result of greater wave action
caused by earlier seasonal melting and reduced size of
the Arctic ice pack, which warrants further study,” said
USGS scientist Lyle Mars. “Since beaches are absent or
poorly developed along most of the studied coast, there
is little, if any, protection against this increased wave
energy. As a result, the waves undercut the mud-rich
permafrost land, causing it to collapse into the sea.”
Thawing permafrost has another important implication
for the welfare of people and ecosystems. Gases trapped
in permafrost, such as carbon dioxide and methane, are
released when it melts. Those greenhouse gases warm
the atmosphere. Methane is 25 times more potent than
carbon dioxide as a greenhouse gas. If the high northern
latitudes continue warming at current rates, the region’s
soils will release more carbon and methane into the
atmosphere, which may lead to higher temperatures that
fuel a feedback cycle of carbon and methane release and
temperature rise. Thawing permafrost may lead to an
acceleration in the rate of climate warming.
About Landsat
Landsat satellites provide an unparalleled record of
Earth’s varying landscapes to help us understand how
Earth is changing and what those changes mean for
life on our planet. The consistency of Landsat’s data
from sensor to sensor and year to year makes it possible
to trace land cover changes from 1972 to the present.
Landsat sensors have captured over two million digital
images of Earth’s continents and surrounding coastal
regions. These digital images include information from
wavelengths of light both visible and invisible to human
eyes. NASA designs the Landsat Earth-observing satellites; USGS manages the satellites, archives the imagery,
and makes the data available to all interested users.
Landsat Program
http://landsat.gsfc.nasa.gov
http://landsat.usgs.gov
Location of Cape Halkett on Alaska’s northern
coast.
International Permafrost Association
http://www.ipa-permafrost.org
Alaska Coastal Erosion
http://energy.usgs.gov/alaska/ak_coastalerosion.html
Intergovernmental Panel on Climate Change
http://www.ipcc.ch
Monitoring Land Change with Landsat
http://change.gsfc.nasa.gov
Source Reference
Quantitative Remote Sensing Study Indicates Doubling of
Coastal Erosion Rate in Past 50 Years along a Segment of the
Arctic Coast of Alaska
by John Mars and David Houseknecht, both USGS
http://energy.usgs.gov/flash/AKcoastalErosion.swf
For more products like this one:
http://landsat.gsfc.nasa.gov/education/resources.html
(Scroll down to “Landsat Lithographs.”)
LG-2009-2-124-GSFC